针刺信息的外周传入途径是针刺镇痛原理的重要组成部分。实验证明针刺镇痛效应是由深部感受器及其传人纤维受刺激引起的

针刺可以兴奋各类神经纤维

但哪类纤维是传入针刺镇痛信息的

主要有两种看法:(1)认为Ⅱ类纤维与针刺镇痛有关;(2)认为Ⅳ类纤维(C-纤维)In this experiment

the rats treated with capsaicin (50mg/kg) s. c. on day 2 of liqc were used 12 weeks after injcction. The levels of substancc P(SP) in sciatic nerves and dorsal spinal cords were measured with radioimmunoassay to evaluate the extent of C-affercnt fibers damaged by capsaicin. The results as follows: (1) the levels of SP in the sciatlc nerve and the dorsal spinal cord are decreased by 69％ and by 62％ respectively

indicating the degeneration of the primary C-afferent fibers is very massive; (2) the average of basal tailflick latency (immersing in 50°C water) is prolonged 105% as compared with the control; (3) after electro-acupuncture

the average of tail-flick latency of the capsaicin treated rats is increased by 81%

while that of the vehicle treated rats increased by 54％. These data suggest that C-afferent fibers substantially mediate the transmission of noxious thermal stimuli

but is unncccssary for the transmission of acupuncture messagc to induce analgesia.